A recent trend in the computer industry is the development of smaller form factors for portable computers. Recently developed form factors include laptop computers, as well as notebook computers and palmtop computers. As portable computers continue toward smaller form factors, the need for smaller, lighter weight, and less expensive component parts for disk drives increases.
Accordingly, disk drive manufacturers require smaller, lighter, and less expensive rotary actuator motors. A typical disk drive employs a rotary actuator motor to move an actuator for positioning the read/write heads over the disk media. Magnetic flux for the rotary actuator motor is typically generated by a magnetic circuit comprising a return plate and a pair of magnets. The return plate is usually comprised of a top plate, a bottom plate, and several standoffs. The standoffs hold the top and bottom plates apart at a fixed distance to form an air gap for receiving an actuator coil. Typically, a pair of magnets are bonded to the inner walls of the top and bottom plates.
The top and bottom plates as well as the standoffs are constructed of a magnetic permeable material such as steel. The top and bottom plates along with the standoffs form a flux return path for the magnetic field generated by the magnets. The magnetic flux density within the air gap between the magnets causes movement of the actuator when an electric current flows in the actuator coil.
However, such prior art return plate designs require fabrication of up to five parts merely to form the flux return path for the rotary actuator motor. Also, such prior art designs require extra manufacturing steps to assemble the return plate. The extra steps to fabricate the return plate component parts, along with the extra assembly steps required to assemble the return plate increases the cost of the disk drive. Also, the extra fabrication and assembly steps increases the likelihood of manufacturing errors. Moreover, the manufacturing tolerances of each component part of the return plate compound for the assembled return plate and result in increased manufacturing errors.
Further, prior art return plate designs require an extra assembly step to align a magnetic latch to the latch tab which is attached to the actuator. The extra assembly step increases the cost of the disk drive and increases the likelihood of manufacturing errors.